1. Field of the Invention
This invention relates to a scroll-type fluid apparatus suitable for use as a gas compressor, gas expander or liquid pump for raising the pressure of air, gas or refrigerant.
2. Description of the Prior Art
Scroll-type fluid apparatus generally including scroll-type compressors, expanders and pumps are well known to those skilled in the art.
Generally, such scroll-type fluid apparatus comprises two scroll members juxtaposed against each other, with each scroll member including an end plate and an involute or spiral wrap disposed in upright position on the end plate. Means, generally referred to as Oldham's ring, are provided for preventing use of the two scroll members from rotating on its own axis, with such means being interposed between the two scroll members so that the one scroll member may move in orbiting motion without rotating on its own axis while the other scroll member remains stationary. The stationary scroll member has a high pressure port formed in the center of its end plate, which port serves as an outlet port when the apparatus functions as a compressor and pump and as an inlet port for the working fluid for producing power when the apparatus is used as an expander. The stationary scroll member is also formed with a low pressure port which is disposed outwardly of the wrap. A fluid pressure is applied to the back (on a side of the end plate opposite the wrap) of the orbiting scroll member, to prevent the two scroll members from moving away from each other.
The pressure of the fluid confined between the two scroll members acts on a point which has a height of one half a height of the wraps, and a force causing one of the scroll members to move in orbiting motion (when the apparatus functions as a compressor and pump) and a load (when it functions as an expander) act on a power transmission between the orbiting scroll member and a crank shaft. The power transmission is disposed on a side of the end plate of the orbiting scroll member opposite the wrap, so that this point is axially spaced apart from the point on which the pressure of the fluid acts and the forces acting on these two points are oriented in opposite directions. Thus, a moment is exerted on the orbiting scroll member and strong local forces urge the orbiting scroll member against the fixed or stationary scroll member.
As the orbiting scroll member is pressed locally with a strong force, the problem of wear caused on the contacting sliding surfaces of the two scroll members is raised. Also, there is a loss of power due to friction increases. Since the two scroll members are not maintained in intimate contact with each other on the entire contacting sliding surfaces and they are in contact with each other locally, no satisfactory seal can be provided to the high pressure port side, the low pressure port side, and between working chambers.
Meanwhile the pressure of the fluid confined between the two scroll members may give rise to a force which tends to urge the two scroll members axially away from each other. U.S. Pat. No. 4,065,279 granted prior to the filing of this application discloses a hydrodynamic thrust bearing intended to bear this force.
It is noted, however, that no reference is made in U.S. Pat. No. 4,065,279 to the fact that the force urging the scroll members against one another becomes locally high or that the urging force becomes biased, nor is there any disclosure of means for solving these problems.